A Research Career Award would support on-going NIH-funded investigations of basic biobehavioral processes in infant rats, especially concerning behaviora] and physiological mechanisms of thermoregulatory and cardiovascular homeostasis. These investigations have resulted in substantial reinterpretations of the thermoregulatory competence of infants during cold challenge and the vital connections between thermoregulation and cardiovascular function. As these investigations have advanced over the last decade, the applicant has used sleep/wake activity as one among many measures of thermoregulatory competence. These studies led naturally to questions concerning the phenomenology and function of active sleep, which, despite its ubiquity in infant mammals, continues to receive relatively little experimental and theoretical attention. Thus, the study of sleep has become an increasingly important focus in the applicant's laboratory, and he has developed new methods and concepts for studying infant sleep from a uniquely developmental perspective. An RCA Award would foster the applicant's ability to advance a program of research to address the neural substrates and function of active sleep in infant rats. The applicant proposes to build on recent investigations from his laboratory to examine systematically the development of active sleep using a variety of methodological approaches (e.g., lesions, neural recording). The developmental framework adopted in this proposal differs from that adopted by other investigators in that it does not judge infant sleep against an adult standard (a theme that has guided his other investigations of homeostasis in infants) but rather seeks to understand the processes of change as sleep becomes increasingly complex and stable over developmental time. These experiments will help to establish the infant rat as an ideal model for understanding the neural processes underlying behavioral state organization. A second aim of this part of the proposal is to integrate whisker activity as an additional component of active sleep in infant rats and to develop the whisker barrel system as a model system for examining the role of sleep-related spontaneous activity in the development of the topographic maps that characterize the barrel system. Therefore, by focusing on such fundamentally important processes as homeostasis and sleep within a common developmental framework, the investigations that would be supported by an RCA Award will have significant consequences for our understanding of normal and abnormal development.